Robert Gates is set to unveil his defence budget and strategy
The US military must shift its focus to fighting a wide range of threats - from cyber attacks to terrorism - the Pentagon's 2010 draft strategy says.
The quadrennial defence review - set to be unveiled in Washington - revises the previous objective of being equipped to fight two major conflicts at any time.
The strategy accounts for threats such as cyber attacks, global warming and "hybrid" guerrilla-style insurgencies.
It comes on the same day that the US defence secretary unveils his budget.
Robert Gates' proposed 2011 spending plan comes to more than $700bn (£440bn), a modest 2% increase, the draft documents show.
But it avoids the sweeping cuts to major weapons programmes seen in last year's budget.
The Pentagon is mandated by Congress to review America's defence priorities every four years.
Jonathan Beale, BBC News
The 2010 Quadrennial Defence Review will show the continuing evolution of military thinking - away from conventional warfare to the increased threat from non-state actors, like al-Qaeda.
China is still seen as a problem - but the wars in Afghanistan and Iraq have forced the US military to focus on the actual enemy, more than potential threats. That will be reflected in defence spending.
More money will be spent on special forces helicopters and drones or UAVs (unmanned aerial vehicles) - the equipment the army needs now, rather than what it might need in 20 years time.
Robert Gates is lucky - while President Barack Obama is putting the squeeze on public spending, defence will be one of the few areas of government that will receive more money.
According to the draft 2010 quadrennial defence review: "It is no longer appropriate to speak of 'major regional conflicts' as the sole or even the primary template for sizing, shaping and evaluating US forces."
It highlights "a multiplicity of threats", including satellite and cyber attacks, as well as terrorist groups and the prospect of more nuclear-armed nations.
But it says the military's top priority is to "prevail in today's wars", citing the need to "dismantle terrorist networks" in Afghanistan and Iraq.
The plan allocates new funding for helicopters, unmanned planes and special operations units, which have played a key role in both conflicts.
It outlines a joint Air Force-Navy battle plan to counter the threats from nations such as China, Iran and North Korea, citing their increasingly sophisticated aerial defence and strike systems.
The report says Mr Gates will also seek to overhaul the military's acquisitions system so the US can get key supplies quickly to its own bases and those of its partners around the world.
The review for the first time identifies global warming as a potential trigger of instability or conflict around the world.